There are various systems and methods for sensing the position of a movable element within a vessel, among them the sensing of the position of a piston within a cylinder, such as a pressurized vessel.
The difficulty is in the sensing of a movable element that travels a relatively long distance and that distance needs to preferably be reduced to a relatively short linear path so that a short range transducer can be used to determine and sense the position of long range movable element by measuring a short linear path.
A precision sensor system that very effectively accomplishes the aforesaid object has been developed for sensing of the position of a movable element and that system is shown and described in U.S. Pat. No. 7,290,476 of Richard Glasson, entitled “Precision Sensor For a Hydraulic Cylinder”. While the system disclosed in that patent is precise, well proven and valuable, one requirement is in the need for high pressure seals since the hydraulic cylinder may be under a substantial pressure and the sensing system components, such as the wiring, needs to pass from the high pressure environment within the cylinder to the ambient pressure exterior of the cylinder.
In the aforementioned Glasson '476 patent, there is a unique linear to rotary to linear wire extensometer mechanism, or converting mechanism, that allows long linear distances to be measured with the use of a short range transducer, such as a linear variable differential transducer (LVDT). Such systems have many uses, such as in hydraulic cylinders and hydraulic accumulators where the installation of a long linear sensor is not practical or technically prudent.
While useful in a large number of hydraulic cylinder and accumulator applications, there are some application cases in which the precision sensor of the Glasson patents could be improved through the substitution of a different type of short-range transducer (other than the LVDT).
In particular, with the system as described in the aforesaid patents, in high pressure applications, some of the electrical wiring is located inside the pressurized vessel and therefore subjected to the rigorous conditions and operating environment within the vessel. In addition, those wires require specialized wire connectors to allow the wires to pass through the cylinder wall to the exterior ambient pressures. Further, in the system of the Glasson patent, for some applications, the sensor is subjected to water, aqueous, ionic or corrosive liquids and, additionally, necessitates an external signal-conditioning electronic module.
It would be, therefore, advantageous to have an improved system and method that uses the efficient converting mechanism with a linear to rotary to linear draw wire extensometer system and to improve the performance and uses of the sensor, even for difficult or hazardous environments.